Steering columns generally comprise a shaft, one end of which is secured to a steering wheel that drives it and is turned by the driver of the vehicle and the other end of which is secured to mechanical components the role of which is to perform the angular positioning of the wheels of the vehicle. The steering column shaft is mounted such that it can rotate in a tubular housing via two rolling bearing assembly devices each comprising a rolling bearing, generally an angular-contact ball bearing, which are mounted in opposition.
The rolling bearing assembly generally comprises an inner race, an outer race, each race being provided with a raceway and a row of rolling elements which is arranged between the two raceways of the races. The rolling bearing assembly is mounted in the housing via its outer race and on the shaft directly or via a sleeve or a ring known as a tolerance ring. A tolerance ring provides the interface between the shaft and the inner race of the rolling bearing and compensates for any geometric defects there might be between these two components. The tolerance ring allows the rolling bearing assembly to be mounted easily on the shaft without initial clamping effect.
Preferably, the assembly operates with no clearance thanks to an axial preload applied to the tolerance rings by an axially elastic member which may, for example, be a spring or a spring washer.
Thus the internal clearance within the rolling bearings is taken up, and permanent contact between the races and the rolling elements of the rolling bearing assembly is ensured.
Reference may be made on this subject to document EP 1 184 583 which describes a rolling bearing assembly device comprising an inner race, an outer race, a row of rolling elements which is arranged between the races, a tolerance ring that provides the connection between the shaft and the inner race and an axial preload elastic element. The elastic element is a washer comprising three crinkles, each bearing axially against the tolerance ring, and comprises fixing tabs for attachment to the inner race.
However, such a rolling bearing assembly device is complex to use and does not allow good distribution of axial preload over the inner race.
Reference may also be made to document WO 01/69098 which describes, in a first embodiment, a rolling bearing assembly comprising an inner race, an outer race, a row of rolling elements which is arranged between the races, a tolerance ring providing the connection between the shaft and the inner race, a damping element and a crinkle washer which is arranged axially between one radial surface of the tolerance ring and the damping element. The crinkle washer allows an axial preload to be applied. That document describes another embodiment in which the damping element comprises a metallic insert and a plurality of studs directed towards the radial surface of the tolerance ring, so that the crinkle washer can be omitted.
However, such rolling bearing assembly devices comprise a plurality of components and a damping element which is complicated to produce. Furthermore, because the axial dimension of the damping element exceeds the axial dimension of the tolerance ring, such a rolling bearing assembly device is not sufficiently compact in the axial direction. Finally, the distribution of axial preload over the inner race is not over the entire periphery of the inner race.